The Mousetweaks package provides mouse accessibility enhancements for
the GNOME desktop.  These enhancements are:
  * It offers a way to perform the various clicks without using any
    hardware button.
  * It allows users to perform a right click by doing a click&hold
    of the left mousebutton. (For a left-handed mouse user, the termes
    left and right have to be inverted.)
  * It provides an applet that the user can install on a panel. This
    applet creates an area on the panel into which the pointer can be
    captured until the user releases it with a predefined button and
    modifier combination.

The options can be accessed through the Accessibility tab of the Mouse
Preferences of GNOME Control Center or through command-line.
